Many conventional methods for growing and recovering cells have been proposed. However, almost all of the methods employ a dish (culture dish), and the number of cells that can be grown is limited. Furthermore, when a thermosensitive polymer is used as a culture substrate, cells grow and are recovered in the form of a sheet or a spheroid within or over a polymer gel, which is different from the actual state in which cells exist. Methods for recovering cultured cells by virtue of a change in environmental temperature using a thermosensitive polymer are described in detail in, for example, Patent Publications 1 to 3.    (Patent Publication 1) JP-A-2-211865 (JP-A denotes a Japanese unexamined patent application publication.)    (Patent Publication 2) JP-A-5-38278    (Patent Publication 3) JP-A-5-244938
Furthermore, with regard to a method for culturing cells using a bioreactor, since in many conventional methods the flow of a supplied culture medium is not of a radial flow type, if a large amount of tissue such as bacteria or cells is immobilized, it is difficult to supply sufficient nutrient and oxygen, control of their concentration is also difficult, and it is therefore difficult to avoid the tissue such as bacteria or cells necrotizing. A radial flow type bioreactor has been introduced in, for example, Non-Patent Publication 1 below.    (Non-Patent Publication 1) S. Mizutani, ‘Bioscience and Industry’, Vol. 48, No. 4, p. 337-342 (1990)
The present inventors have also proposed that the cell adhesion and biocompatibility of a cell culture membrane can be improved by, for example, hydrophilizing the surface of a porous sheet-form material using a polyamino acid urethane copolymer (Patent Publication 4). However, a way in which these conventional techniques could be combined in order to totally overcome various problems of the conventional techniques has not been examined or proposed.    (Patent Publication 4) JP-A-2001-136960